We propose to examine the interaction of ATP and its metal chelates with ATP utilizing enzymes, in particular nitrogenase. The interactions will be measured by use of a system of direct scanning of chromatography columns during gel filtration of the interacting components. Construction of an improved system for such scanning is a major objective of the proposed work. We will use a rapid transport of the optical system coupled to a rapid data acquisition system so that the changes of hydrodynamic properties of proteins can be monitored over relatively short time intervals. Hexokinase will be used as a model system for development of the scanning system since it is known to undergo association-dissociation reactions as a function of pH and the concentration of substrates. The scanning system will then be used for examination of the interaction of nitrogenase components in the presence and absence of ATP.